Fifth wheel

ABSTRACT

A fifth wheel assembly (10) comprising a lower support structure (12) adapted to be mounted on the chassis of a prime mover and an upper support plate (13) upon which a trailer is to be supported, and between which a cam operated linkage mechanism is incorporated which has a pair of space apart main link assemblies (14) pivotally attached at one end (19) to the lower support structure and pivotally attached adjacent their other ends (13) to the upper support plate. Cam members (15) are pivotally supported on the link assemblies with their cam surfaces in contact with the lower support structure, whereby rotation of the cam members pivots the link assemblies upwardly about their pivotal connections to the lower support structure to thereby raise the upper support plate attached to the other ends of said link assemblies. A pair of spaced apart strut assemblies (20) are also provided pivotally connected at one end (21) to respective ones of the main link assemblies and detachably connected at their other ends, to the lower support structure via a pin (28) extending through a number of alternative arrangements of aligned holes (23, 24, 25, 26, 27), and such as to hold said upper support plate relative to the lower support structure in one of a number of alternative positions.

TECHNICAL FIELD

This invention relates to a fifth wheel or turntable for an articulatedvehicle, such as a semi-trailer, and more particularly relates to anadjustable height fifth wheel.

BACKGROUND ART

The height of the chassis for some makes of primer-movers differ fromother makes, whilst the height of trailers also varies. It is alsocommon practice for prime-movers to be coupled to a variety of trailersover a period of time in mixed fleet situations, rather than there beinga continuing prime-mover/trailer combination. With such operatingrequirements the use of static fifth wheels will not ensure a relativelylevel load supporting surface on the trailer.

In the past mechanisms to enable adjustment of the height of the fifthwheel to deal with the above problems have necessitated hydraulic andpneumatic lifting arrangements all of which are costly.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a fifthwheel assembly for mounting on a prime-mover and incorporating arelatively inexpensive and easily operated elevating mechanism.

The invention therefore envisages a fifth wheel assembly comprising alower support structure adapted to be mounted on the chassis of aprime-mover and an upper support plate upon which a trailer is to besupported, wherein between said support structure and said support platea cam operated linkage mechanism is incorporated to raise and lower theupper support plate relative to the lower support structure, and whereindetachable means are provided to hold the upper support plate relativeto said lower support structure in one of at least two alternativepositions.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention will now be described with reference tothe accompanying drawings in which:

FIG. 1 is a perspective view of the assembly of this preferredembodiment;

FIG. 2 is a side elevational view of the assembly of FIG. 1 showing theassembly in its lowest height position;

FIG. 3 is a side elevational view of the assembly in one of a pair ofintermediate height positions;

FIG. 4 is a side elevational view of the assembly in its highest heightposition; and

FIG. 5 is a plan view of the assembly of the previous figures.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings the fifth wheel assembly designated as 10,comprises a lower support structure 12 and an upper support plate 13 asare conventional for fifth wheel assemblies. Incorporated between thestructure 12 and the support plate 13 is a cam and linkage assemblyincorporating a pair of spaced apart main link assemblies 14 pivotallymounted at 19 on the support structure 12 and between a pair ofupstanding support lugs 19a as shown. A pair of cam members 15 arerotatably supported on each of the link assemblies 14 and carried bypivot shafts 16 through the link assemblies 14. The peripheral surfacesof the cam members 15 engage the support structure 12 such that whenrotated by the handles 17, fixed to the other ends of the pivot shafts16, the link assemblies will pivot up and down to raise and lower thesupport plate 13 to which portions 18b of the link assemblies towardsthe opposite ends thereof are pivotally connected at 18 between a pairof lugs 18a extending downwardly from beneath generally diametricallyopposed edge portions of the support plate 13. As shown a commonconnecting bar 16a may be coupled between the cam members.

Additional link assemblies 20 acting as struts are pivotally connectedat 21 to the extreme ends of the link assemblies 14, or alternatively tosaid upper support plate, with the lower ends of the additionalassemblies 20 interlocking in a number of positions with a pair ofspaced apart locating bars 22 supported on the support structure 12 andhaving in this case three aligned pairs of holes 23, 24 and 25therethrough adapted to align with one or the other of a pair of holes26 and 27 in the additional link assemblies with a locating pin 28 withhandle being inserted through the aligned holes for each location tohold the assembly at that location.

At the lowest height of the assembly for the fifth wheel and as shown inFIG. 2, the holes 23 in the locating bar and the holes 27 in the linkassemblies are aligned and the locating pins 28 inserted.

In a first elevated position (not shown), the holes 26 in the linkassembly are aligned with the holes 25 in the locating bars, andlocating pins 28 inserted.

In the second elevated position as shown in FIG. 3, the holes 26 in thelink assemblies are aligned with the holes 24 in the locating bars, andlocating pins 28 inserted.

In the third or highest elevated position as shown in FIG. 4, the holes26 in the link assemblies are aligned with the holes 23 in the locatingbars, and locating pins 28 inserted.

At any position, after insertion of the locating pins 28, the cam member15 and their handles 17 can be swung back down to the positions shown inFIGS. 1 and 2.

We claim:
 1. A fifth wheel assembly comprising a lower support structureadapted to be mounted on the chassis of a prime mover and an uppersupport plate upon which a trailer is to be supported, wherein betweensaid support structure and said support plate a linkage mechanism isincorporated and has a cam member eccentrically mounted for rotationabout an axis extending transversely of the linkage mechanism with itsperipheral surface engaging the lower support structure whereby, whenrotated in one direction, the distance between the rotation axis and thepoint of engagement with said lower support structure progressivelyincreases to extend the linkage mechanism, whereas, when rotated in theopposite direction, the said distance decreases to retract the linkagemechanism, such that the upper support plate is raised and loweredrelative to the lower support structure, and wherein detachable meansare provided to hold the upper support plate relative to said lowersupport structure in one of at least two alternative positions.
 2. Afifth wheel assembly as claimed in claim 1, wherein said linkagemechanism comprises a pair of spaced apart main link assembliespivotally attached at one end to the lower support structure andpivotally attached adjacent their other ends to said upper supportplate, said cam member being pivotally supported on at least one of saidlink assemblies.
 3. A fifth wheel assembly as claimed in claim 2,wherein said detachable means comprises a pair of spaced apart strutassemblies pivotally connected at one end to respective ones of saidmain link assemblies, and detachably connected to said lower supportstructure to hold said upper support plate relative to said lowersupport structure in one of at least two alternative positions.
 4. Afifth wheel assembly as claimed in claim 3, wherein said strutassemblies cooperate with locating members supported on said lowersupporting structure and holes through said strut assemblies and saidlocating members are provided whereby upon alignment of selective holesand insertion of a locating pin said strut assemblies will hold saidupper support plate relative to said lower support structure in said oneof at least two alternative positions.